A canine model will be utilized, in an attempt to reproduce a progressive and fatal peritonitis which mimics the pathophysiology of severe clinical sepsis. As sepsis develops, frequent measurements will be made of cardiovascular, respiratory and oxygen utilization to: (1) document the validity of the model and (2) relate these changes to effects on metabolism, catecholamines, coagulation, serum complement, liver and renal function. The dog model will be prepared by implanting a Swan-Ganz pulmonary arterial catheter and a systemic arterial catheter. Another catheter will be implanted in the devascularized obstructed gallbladder. After 48 hours, frozen, processed human feces mixed with barium sulfate will be injected under pressure into the gallbladder. Control studies will require two groups: (1) exploratory laporatomy and (2) injection of saline into the devascularized, obstracted gallbladder. Daily X-rays will be obtained of the septic group to determine onset of gallbladder disruption. If unruptured within 48 hours, the animal will be given a light anesthetic and the gallbladder ruptured wih saline volume expansion. This produces peritonitis with death of the dog within 2-3 days. Baseline and daily studies will be obtained for insulin, glucagon, lactate, pyruvate, catecholamines, SMA-12, total serum complement, CBC, platelets, fibrinogen, serum osmolality, arterial-venous oxygen tension and content, carbon dioxide and pH. Urine creatinine, osmolarity and hourly urine volume will be measured. Cardiac output, central venous pressure, systemic arterial pressure, pulmonary artery and pulmonary catheter wadge pressures will be obtained. Following gallbladder disruption. the study will be obtained twice daily. Wedge pressures will be maintained through the study at 5 mmHg. Control animals will be sacrificed on the fifth study day. All animals will have post-mortem examinations. An attempt will be made to modify the pathophysiology with prostaglandin cyclo-oxygenase blocker, vasoactive agents and pharmacologic doses of methylprednisone.